Conventional antenna arrays for wireless communication systems comprise multiple antenna elements. The antenna arrays are often used with existing Node-B equipment in most cellular installations and utilise a fixed 65° beam pattern. Outside of the main lobe of the antenna beam the signals are spatially filtered and significantly attenuated. Conventional network planning and passive antenna array solutions process all incoming signals with a common fixed beam pattern. Such receive processing, based on signals received within the geographic area identified by the antenna beam main lobe, referred to as the RF footprint, tends to dictate a corresponding common beam pattern for transmitter operation. Thus, an identical radio frequency (RF) footprint is used for both receive (Rx) and transmit (Tx) operation.
Receive beam-forming using antenna arrays depends on the ability to constructively add incident signals on each of the antenna elements in a way that coherently adds those from the desired direction. Thus, incident signals that are not from the desired direction will be incoherently added, and thus will not experience the same processing gain. The term ‘coherency’ implies that the signals will have substantially the same phase angle. In addition, thermal noise from multiple sources also exhibits incoherent properties, and thus when added the signals from multiple sources do not experience the same processing gain as a coherent desired signal. Conversely in transmit active antenna arrays the signals are coherently combined within the intended beam pattern as electromagnetic (EM) signals in the ‘air’ so that they arrive coherently at the mobile station (MS) (e.g. user equipment (UE) in third generation partnership project (3GPP™) parlance) receiver.
In the examples herein described, an antenna element is a radiative structure whose purpose is to convert electro-magnetic (EM) signals to electrical signals, or vice versa, in which a singular element has a fixed radiation pattern. The term ‘radiative elements’ described herein refers to elements capable of radiating an electromagnetic signal. Furthermore, the term ‘radiative elements’ described herein also encompasses structures capable of absorbing EM radiation and converting to electrical signals. These elements, constructed as an array can be configured to have various radiation patterns by manipulation of electrical signals coupled to the elements. Thus, the ability to alter the radiative beam shape may be achieved.
For completeness, it is worth clarifying the Antenna Reciprocity Theorem, which in classical treatises on electromagnetic fields and antennas is usually formulated as follows:
Given two antennas ‘A’ and ‘B’ placed at some distance apart, each of them may be operated either as a transmitting antenna or as a receiving antenna. Suppose that antenna ‘B’ is kept intact, whilst the performance of antenna ‘A’ as a transmitter is modified. A consequence of this is that, for a fixed amount of input power, the signal received by antenna ‘B’ changes by a factor ‘F’ due to the change imposed on antenna ‘A’. Then the same modification changes also the performance of antenna ‘A’ as a receiver and does so by the same factor ‘F’. The theorem follows from certain symmetries of Maxwell equations and its validity is easily verified experimentally and has been widely published. Hence, the radiation pattern induced by a transmitter operably coupled to an antenna with same carrier frequency as a receiver has identical azimuthal angular link loss. Thus, the term radiative and ‘radiative beam pattern’ hereinafter may also be applied to a receiver.
An active antenna system (AAS) is a group of antennas emitting signals to produce a directive radiation pattern. Each antenna element is connected to a radio transceiver. The radiation pattern of the array can be controlled by configuring the relative phases and amplitudes of the respective signals at each AAS antenna element. By precisely controlling relative phases and amplitudes of processed signals prior to be being combined, it is possible to align peaks and nulls in the radiated signals to form a beam, a process referred to hereafter as ‘beamforming’.
The phase and amplitude of the signal on a given antenna element is controlled by adjustments within the transceiver. Following installation, and particularly following re-configuration of radio frequency equipment and/or circuits, it is therefore important to know which radio transceiver is connected to which antenna element. Furthermore, a transceiver may be composed of multiple elements, such as Power Amplifier (PA) devices.
In an antenna element array, the number of possible connectivity paths of the antenna elements to the radio transceiver line-ups may be defined as:Nelement×(M1!−(M1−Nelement)!)× . . . ×(Mn!−(Mn−Nelement)!)×L  [1]where:                Nelement is the number of used antenna elements in the system;        M1 is the number of paths through the 1st multipath switch;        Mn is the number of paths through the nth multipath switch; and        L is the number of used radio transceiver line-ups in the system.        
The number of possible paths therefore rises exponentially as the number of multipath switches and paths through each multipath switch increases. If the routing through the system is not as expected for one or more of the antenna elements then the system performance is, at a minimum, degraded and may be, in a worst case scenario, completely non-functional in its beamforming capability. Thus, it is important to know which PA from which transceiver is connected to which antenna element.
Typically, this imposes restrictions on the AAS manufacture and assembly process such that connectivity must be predetermined and the assembly proceeds according to a somewhat inflexible predetermined connectivity.
There may also be a need to account for additional switching elements across the various antenna elements to logical channel paths. Furthermore, there may be a need for dynamic selection of the number of antenna elements that are connected to transceiver radio line-ups for a given configuration of the array.
U.S. Pat. No. 8,265,572 B2 discloses a multiple envelope tracking system for an active antenna array where the premise is that the logical channel routing to individual antenna elements is known and fixed. There is no disclosure of any mechanism by which an antenna array is able to detect the logical to physical element signal routing.
Both U.S. Pat. No. 7,212,838 and U.S. Pat. No. 6,952,455 specifies a method for adapting beam weightings to increase received signal power levels in a system. This receive-only method does not rely on or establish the connectivity between antennas and logical channels in the transmitter or receiver. Moreso, application of this method would interfere with the control of beam direction, as the resultant beam would always be biased towards the highest power source (blind adaptation) rather than intended direction, and beam shapes in general would be unpredictable.
Thus, there is currently no known method of dynamically establishing connectivity between antennas and logical channels in a transmitter or receiver.